Photochemical reaction of cyclohexyl phenyl ketone within lyotropic liquid crystals

Article abstract of DOI:10.1016/j.tet.2007.11.084

Lyotropic liquid crystals (LCs) formed by sodium dodecyl sulfate (SDS), n-pentanol, and H₂O at room temperature in their tertiary phase diagram have been explored as a confined medium for the typical photochemical reaction of cyclohexyl phenyl ketone (1), which can lead to either intramolecular hydrogen abstraction product 2 or intermolecular reduction product 3 in isotropic solutions upon irradiation. Studies on the product distributions of ketone 1 in the absence and presence of electron donors in this work demonstrate that LC not only restricts the movement of the substrates and intermediates but also encapsulates the substrates and electron donors together during photoirradiation, thereby giving rise to the formation of intermolecular hydrogen abstraction product 3 with high efficiency. A comparison of the same reaction in SDS micelle reveals that LC provides much better constraint than the micelles. The solution-like LC can be used as a microreactor to direct the reaction pathway of ketone 1 by controlling the viscosity and close contact between substrates and electron donors.

Full text of DOI:10.1016/j.tet.2007.11.084

Available online at www.sciencedirect.com
Tetrahedron 64 (2008) 1918e1923
www.elsevier.com/locate/tet
Photochemical reaction of cyclohexyl phenyl ketone
within lyotropic liquid crystals
*
Feng-Feng Lv, Xin-Wei Li, Li-Zhu Wu , Chen-Ho Tung
Laboratory of Organic Optoelectronic Functional Materials and Molecular Engineering, Technical Institute of Physics and Chemistry
and Graduate University, The Chinese Academy of Sciences, Beijing 100080, PR China
Received 13 September 2007; received in revised form 21 November 2007; accepted 23 November 2007
Available online 21 December 2007
Abstract
Lyotropic liquid crystals (LCs) formed by sodium dodecyl sulfate (SDS), n-pentanol, and H2O at room temperature in their tertiary phase
diagram have been explored as a confined medium for the typical photochemical reaction of cyclohexyl phenyl ketone (1), which can lead
to either intramolecular hydrogen abstraction product 2 or intermolecular reduction product 3 in isotropic solutions upon irradiation. Studies
on the product distributions of ketone 1 in the absence and presence of electron donors in this work demonstrate that LC not only restricts
the movement of the substrates and intermediates but also encapsulates the substrates and electron donors together during photoirradiation,
thereby giving rise to the formation of intermolecular hydrogen abstraction product 3 with high efficiency. A comparison of the same reaction
in SDS micelle reveals that LC provides much better constraint than the micelles. The solution-like LC can be used as a microreactor to direct
the reaction pathway of ketone 1 by controlling the viscosity and close contact between substrates and electron donors.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
Lyotropic liquid crystals (LCs) that are formed by surfac-
tants in either water or oil, or both of them usually consist
of an amphiphile and a typically aqueous solvent, and possess
highly ordered nanostructures. Lamellar liquid crystals (LLCs)
and hexagonal liquid crystals (HLCs) are the two representa-
tives of LC family.3,4 As shown in Figure 1, the hydrocarbon
chains and the head group of the surfactants compose the
hydrophobic and hydrophilic domains of thermodynamically
stable LC systems, respectively. In LLC, the surfactant
Optimizing selectivity of photochemical reactions is one of
the most important topics of current research since photo-
chemical reactions generally tend to give more than one prod-
uct.1 During the past decades, many elegant and efficient
strategies have been designed toward this goal. The use of
supramolecular systems for selective photochemical reactions
turns out to be one of the successful approaches because the
interactions of substrates with supramolecular systems may
alter the photochemical behaviors of the confined substrates,
and thus may direct the photochemical reaction to the desired
product(s).2 It has been known that photochemical reactions
in isotropic solutions and supramolecular systems often lead
to different product distributions or in some cases, totally dif-
ferent products.1,2
* Corresponding author. Tel./fax: þ86 10 82543580.
E-mail address: lzwu@mail.ipc.ac.cn (L.-Z. Wu).
Figure 1. Schematic representative structures of the liquid crystals.
0040-4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.11.084

F.-F. Lv et al. / Tetrahedron 64 (2008) 1918e1923
1919
molecules aligned orderly (on average) with their long axes
parallel to one another affording a compact structure.
Alternatively, the oriented rod-like surfactant molecules in
HLC lead to a helical column. The viscosity and compaction
of HLC have been known to be much higher than that of
LLC.3 These unique features of LC have recently been of great
interest for the templates of various ordered inorganic and
organic nanostructures.5,6 In this report, we are particularly in-
terested in the photochemical reactions within LC because the
large interfaces and hydrophobic and hydrophilic domains
present in the LC are expected to increase the local concentra-
tion of substrates, and even to mediate their orientations. More
importantly, the high viscosity and compact structures are
believed to restrict the movements of both substrates and
intermediates greatly. As a result, the optically transparent
supramolecular assemblies may be amenable to selective photo-
chemical investigations.
Previous work in this area was mainly focused on the thermo-
tropic liquid crystals that are formed by certain organic mole-
cules through heating.7,8 Weiss and Nerbonne took the lead in
developing the photochemical reactions in liquid crystals.7a
They found that the cholesteric liquid crystals could influence
the efficiency of photodimerization of acenaphthylene largely.
Later on, Turro et al. investigated the photolyses of dibenzyl
ketones in thermotropic liquid crystals.7b They rationalized
the relatively low cage effects observed by the fact that the prob-
ability of recombination of benzyl radical pairs from decarbon-
ylation of 1-(4-methylphenyl)-3-phenylpropan-2-one is very
sensitive to the nature of the local solvent organization even
though the thermotropic liquid crystals are very viscous. Photo-
chemical asymmetric induction in chiral liquid crystals has also
been explored, but the obtained optical yields are generally low.8
Compared with thermotropic liquid crystals, lyotropic liquid
crystals (LCs) can be prepared at ambient temperature and are
easier to manipulate photochemical studies. To examine
whether LC could be used as a confined medium for selective
photochemical reactions, the typical reaction of cyclohexyl
phenyl ketone (1),9,10 which can lead to either intramolecular
hydrogen abstraction product (2) or intermolecular reduction
product (3), in isotropic solutions upon irradiation, was investi-
gated in this work (Scheme 1). It was noted that product 3 is
formed as the major product in the presence of electron donors
within LC, while product 2 is mainly produced in most micellar
cases under the same conditions. These results demonstrate that
LC including both LLC and HLC not only restricts the move-
ment but also encapsulates the substrates and electron donors
together during photolysis, and thus leading to the formation
of intermolecular hydrogen abstraction product 3 with high
efficiency. A comparison of the same reaction in sodium dodecyl
sulfate (SDS) micelle reveals that LC provides much better
constraint than the micelle. By controlling the viscosity and
close contact between substrates and electron donors, a new
type of microreactor has been established.
2. Results and discussions
2.1. Preparation of LC samples for irradiation
Lamellar liquid crystals (LLCs) and hexagonal liquid crys-
tals (HLCs) used in this work were prepared by sodium dodecyl
sulfate (SDS), n-pentanol (C5H11OH), and H2O at room tem-
perature in their tertiary phase diagram,4 in which SDS
1.875 g, C5H11OH 1.250 g, and H2O 1.875 g were used for
LLC and SDS 1.875 g, C5H11OH 0.313 g, and H2O 2.813 g
for HLC. Appropriate amounts of components, including LC,
substrates, and/or electron donors, were added into a Pyrex
tube, and stirred for 10e20 h till the mixture became a uniform
transparent system to make the samples for photoirradiation.
Because the product distributions are always the same as the
ratio of electron donors to 1 beyond 7:1, we set the ratio as
7:1 to guarantee many electron donors around one substrate.
Namely, the substrate loading level was kept at 1 mg of ketone
1 in 1 g of LC. The texture patterns of the prepared samples
were examined by a polarizing microscope. Similar to that
pure LC,3 the LLC was formed as maltese cross textures, while
HLC was formed as focal conic textures (Fig. 2). These obser-
vations suggest that the LC phases remain unchanged when the
substrates and electron donors were added under the conditions
investigated.
2.2. Photochemical reaction of 1 within LC
in the absence of electron donors
The photoreaction of cyclohexyl phenyl ketones (1) is a
well-known reaction (Scheme 1),9,10 which gives 1-phenyl-
hept-6-en-1-one (2) and a-cyclohexyl benzyl alcohol (3) upon
irradiation of 1 in organic solvents. Product 2 comes from the
intramolecular hydrogen abstraction (Scheme 2), in which
hydrogen abstraction occurs via a six-membered ring transition
state. Alcohol 3 arises from the electron-transfer-initiated
intermolecular photoreduction (Scheme 3). Evidently, the
intermolecular photoreduction may be facilitated when electron
donors are introduced. Furthermore, the ratio of 2 to 3 is very
sensitive to the solvents used. It was reported9 that in
degassed benzene 2 and 3 were present in a 3:1 ratio, while in
1-propanol irradiation of 1 resulted in much rapid formation
of 2, but quickly changed the ratio to 30:1 at low reaction
conversion.
The photochemical reaction of ketone 1 within LC was per-
formed at room temperature in this work. Typically, the blank
Pyrex tube was connected to a vacuum system through a stop-
cock adapter to remove air by three freezeethaw cycles before
irradiation. The mixture was extracted with ether for further
gas chromatograph (GC) detection after irradiation with
a 500 W high-pressure Hanovia mercury lamp. The photo-
chemical behavior of 1 within LC is summarized in Table 1.
It was found that the efficiency of the typical photoreaction
is extremely higher as compared with that in hexane solutions.
O
O
H
OH
HO
H
hv
N2
2
3A
3B
1
Scheme 1.

1920
F.-F. Lv et al. / Tetrahedron 64 (2008) 1918e1923
Figure 2. Polarized light micrographs of liquid crystals made of SDS/C5H11OH/H2O.
We employed pyrene as the probe to determine the micro-
O
Ph
O
OH
PhC
C
H
OH
PhC
polarity of the LC interior. It is well established that the ratio
of intensities of the vibrational peaks of 1 and 3, namely I1 and
I3, in the fluorescence spectrum of pyrene is an excellent mea-
sure of polarity of its immediate environment.11 Table 2 pre-
sented the I1/I3 values of pyrene in aqueous LC media. A
comparison of the I1/I3 of LC with that of common solvents
indicates that the polarity experienced by pyrene in LLC and
HLC is similar to that of ether, while that in micellar solution
is very close to that of 1-propanol. Evidently, the polarity of
the microdomains within HLC and LLC is similar but more
hydrophobic than that of the micelles. Additionally, excimer
emission from pyrene could not be observed both in LC and
hv
N2
Scheme 2.
3*
O
O
hv
ISC
R
R
RRHC R1
1 °or
N
H
2 ° amine
Table 1
Product distributions of 1 in the absence and presence of electron donors
within LC
O
RRHC R1
N
R
Entry Electron donor
Reaction media Molar ratio % ee in 3
of 2/3a
H
1
2
3
4
No
No
1-Propanol
Ether
Ether
30:19
3:1
1:2
3:1
3:1
30:1
1:12
1:3
1:2
1:6
1:3
1:2
1:2
1:2
1:1
2:1
2:1
3:1
2:1
3:1
0
0
(ꢀ)-Prolinol
0
No
HLC
LLC
Micelleb
HLC
LLC
0
OH
0
RRC R1
N
R
0
5
6
7
8
(ꢀ)-Prolinol
4Bc
4B
0
H
5
Micelle
HLC
LLC
(ꢀ)-Ephedrine
4B
4B
0
OH
*
H
Micelle
R
N
RRC
(ꢀ)-N-Methylephedrine HLC
4B
4B
0
R1
LLC
Micelle
HLC
LLC
Scheme 3.
(þ)-Norephedrine
5A
5A
0
To avoid secondary reactions, the irradiation time was kept
less than 5 min for all the samples studied in LC (conversion
30%). Some important features are worthy of noting based
on the correlated calculation of the product ratio. In contrast
to that obtained in micelle (30:1), the ratio of intra- and inter-
molecular products (2/3) was found to be 3:1 in both LLC and
HLC. Clearly, the intramolecular reaction is hampered within
LC as compared with that in micelle.
Micelle
HLC
HLC
9
(ꢀ)-Menthol
(ꢀ)-Proline
d
d
10
a
Conversion was estimated by GC using hexadecane as the internal standard
and was controlled at less than 30%.
b
The concentration of ketone 1 and electron donors was set to 1:7 in
micelle, LLC, and HLC.
c
A represents the first peak of the two enantiomers observed in GC and B
refers to the second one.

F.-F. Lv et al. / Tetrahedron 64 (2008) 1918e1923
1921
Table 2
I1/I3 Ratio of pyrene within LC and common solvents
(a)
HLC
Medium
I1/I3
HLC
LLC
0.97
0.99
1.11
0.98
1.09
0.93
1.87
Micelles
Ether
1-Propanol
1-Pentanol
Water
micelle at the concentration studied, suggesting that pyrene
molecules are isolated from each other in LC, namely, one
molecule of pyrene in the excited singlet state is unable to
meet the other one in the ground state within the excited-state
lifetime (Fig. 3). A comparison of the reaction occurred in
ether and 1-propanol, we found the product distribution of
photoirradiated 1 in LC and micelle should not be only related
to the polarity of the domains (Table 2). Since the intramole-
cular hydrogen abstraction occurs via a six-membered ring
transition state (Scheme 2),9 the viscous media of LLC and
HLC may restrict the movement of substrate 1, and suppress
the formation of the rigid transition state to some extent. On
the contrary, the relatively flexible micelles allow substrate
1 to adopt the conformation suitable for hydrogen abstraction,
leading to the formation of intramolecular product 2
predominantly.
350
400
450
500
wavelength (nm)
(b)
LLC
2.3. Photochemical reaction of 1 within LC
in the presence of electron donors
350
400
450
500
wavelength (nm)
It is of significance that in the presence of electron donors
the ratio of 2/3 is altered dramatically in LC as compared with
that in micelle (Table 1). The photoreduction intermolecular
product 3 could be formed as the major product in LC, while
the intramolecular product 2 still dominates in micelle in most
cases. In particular, a significant selectivity (3/2¼12:1) in
HLC, even higher than that observed by Ramamurthy et al.
in zeolite (3/2¼5:1),10b could be achieved when electron
donor of (ꢀ)-prolinol was present (Fig. 4). As we know, the
photoreduction of ketone 1 by electron donor is an electron-
transfer-initiated process (Scheme 3), which involves at least
one electron transfer and two hydrogen abstraction pro-
cesses.9,10 The multistep nature of the reaction requires that
in addition to the redox potential allowance, the molecules
of ketone 1 should be close to the electron donors for a rela-
tively long time. Due to the hydrophobic characteristics and
polar carbonyl group, ketone 1 would prefer to stay in the hy-
drophobic domains near the interface in HLC, as shown in
Figure 5. In this situation, the electron donor of (ꢀ)-prolinol
with similar polarity may be very close to substrate 1. The
remarkable selectivity (3/2¼12:1) obtained in HLC indicates
that such a close contact does not dissociate during the inter-
molecular reduction process. That is to say, the compact HLC
is able to encapsulate the molecules of 1 and electron donors
forming a ‘microreactor’ (Fig. 5a), where the substrate is next
to the electron donors.
(c)
Micelle
350
400
450
500
wavelength (nm)
Figure 3. Fluorescence spectra of pyrene in LC and micelle: [pyrene]¼10 mM;
excited at l¼339 nm.
To shed more light on the microreactor, a series of electron
donors have been investigated (Scheme 4). It is anticipated that
subtle change of structure and electron-donating ability may
alter the product distributions subsequently. Indeed, not all
the electron donors could dominate the formation of intermo-
lecular product 3. With (ꢀ)-prolinol and (ꢀ)-ephedrine as the

1922
F.-F. Lv et al. / Tetrahedron 64 (2008) 1918e1923
(a)
Microreactor
Microreactor
(b)
(c)
Figure 4. GC traces of the product mixtures (Supelco b-dex 325 column) of 1
in the presence of (ꢀ)-prolinol in (a) ether; (b) HLC.
Electron
donor
Cyclohexyl
phenyl ketone
SDS
electron donors, the ratio of 2/3 could be achieved to 1:12 and
1:6, respectively. However, this ratio drops to 1:2 when (ꢀ)-
N-methylephedrine was incorporated. (þ)-Norephedrine and
(ꢀ)-menthol can even change the preference and intramolecu-
lar product 2 was present as a major product (2/3¼2:1) in HLC.
Such a reverse trend observed in the product distributions im-
plies that small changes in the electron-donating ability and
molecular structure of electron donors can influence the selec-
tivity of the photochemical reaction remarkably. Since alcohol
3 is the product of electron-transfer-initiated intermolecular
photoreduction, the rate of the intermolecular reaction should
be related to the electron-donating ability of electron donors.
With reference to the previous work on the photochemical
reaction of ketones,9,10 the photoreduction efficiency should
be in an order of tertiary amineꢁsecondary amineꢁprimary
amine. However, in the case of HLC, the ratio of 3/2 increased
as secondary amineꢁtertiary amineꢁprimary amine when the
ephedrine-like amine was incorporated, respectively (Table 1,
entries 6e8). Considering the compact structure of HLC, this
may be attributed to the relatively bulky tertiary amine that
cannot align with the hydrophobic chains of surfactant very
well, thus affording (ꢀ)-N-methylephedrine a little bit far
from the substrate 1. Similar behavior was also observed in
photoreaction of 1 in (ꢀ)-menthol-incorporated HLC (Table
1, entry 9).
Figure 5. The interaction models of 1 and electron donors within (a) HLC; (b)
LLC; (c) micelle.
between the incorporated electron donors and substrate 1 is,
the higher the ratio of 3/2 will be. The product distribution
in (ꢀ)-proline-incorporated HLC is the same as that observed
in the absence of electron donors in HLC (Table 1, entries 4
and 10), suggesting that (ꢀ)-proline is actually out of the mi-
croreactors in HLC. When carboxyl group replaced hydroxyl
group in (ꢀ)-prolinol, the carboxyl group would decrease
the electron-donating ability of the amine group in (ꢀ)-pro-
line. More importantly, the polar carboxyl group would
*
O
H
N
H
N
*
*
OH
OH
*
OH
*
(-)-prolinol
(-)-proline
(-)-menthol
CH3
H
H
H
H
N
H
CH3
N
H
H
HO
HO
N
CH3
HO
H
H
CH3
CH3
(-)-N-methylephedrine
CH3
(-)-ephedrine
(+)-norephedrine
A comparison of (ꢀ)-prolinol and (ꢀ)-proline mediated
photoreaction further evidenced that the closer the contact
Scheme 4.

F.-F. Lv et al. / Tetrahedron 64 (2008) 1918e1923
1923
move (ꢀ)-proline toward the hydrophilic domains in HLC. In
Acknowledgements
contrast, the similar hydrophobic property and polarity render
(ꢀ)-prolinol and substrate 1 stay in the microreactors in prox-
imity. As a result, the highly viscous HLC strictly prevents ex-
cess (ꢀ)-prolinol around 1 escaping from the microreactors
(Table 1, entry 5), thereby guarantees the reaction occurrence
with highest selectivity and large rate acceleration.
We are grateful for the financial support from National
Science Foundation of China (Nos. 20333080, 20332040,
20472091, 50473048, 20472092, 20403025, and 20672122),
The Ministry of Science and Technology of China (Grant
Nos. 2004CB719903, 2006CB806105, G2007CB808004 and
2007CB936001) and The Bureau for Basic Research of the
Chinese Academy of Sciences.
The changes in product distributions are also pronounced in
LLC but less than that in HLC. In view of the surfactant mol-
ecules aligned orderly (on average) with their long axes paral-
lel to one another, the substrate and the excess electron donors
would also reside in the ‘microreactors’ (Fig. 5b). Neverthe-
less, the softer walls of LLC may allow the substrate and elec-
tron donors to diffuse along the long axes slowly, resulting in
the ratio of 3/2 in LLC lower than that in HLC. Similarly, the
more flexible micelles show much weaker restriction in the
product distributions of all the cases under the same condi-
tions. In addition, the intramolecular hydrogen abstraction
may be favored to some extent in the looser microreactors
present in micelles.
Evidently, the ordered viscous LC can encapsulate the sub-
strate and electron donors together during photoirradiation. By
controlling the viscosity and close contact between substrates
and electron donors, the solution-like LC can be used as a
microreactor to direct the reaction pathway of ketone 1. Nev-
ertheless, the ee values for the intermolecular hydrogen ab-
straction product 3 obtained in this study were less than 5%
(Table 1). Such a low stereoselectivity should be related to
the multistep nature of the intermolecular photoreduction,9,10
in which both ketone 1 and the intermediate radical 5 possess
pro-chiral faces (Scheme 3). Although the LC is stiff enough
to restrict the translational motions of ketone 1 and the chiral
electron donors affording product 3 with high efficiency, it
cannot control their rotation efficiently. Moreover, the pro-chi-
ral faces of both ketone 1 and the intermediate radical 5 allow
subtracting hydrogen from their surrounding environment,
rather than from the chiral inductor, thereby resulting in low
enantioselectivity observed. To this end, we are actively per-
forming the photochemical reactions with simple intermedi-
ates in LC and willreport examples in due course.
References and notes
1. (a) Photochemistry in Constrained and Organized Media; Ramamurthy,
V., Ed.; VCH: New York, NY, 1991; (b) Molecular and Supramolecular
Photochemistry; Ramamurthy, V., Schanze, K. S., Eds.; Marcel Dekker:
New York, NY, 1999; Vol. 3; (c) Chiral Photochemistry; Inoue, Y.,
Ramamurthy, V., Eds.; Marcel Dekker: New York, NY, 2004.
2. (a) Weiss, R. G.; Ramamurthy, V.; Hammond, G. S. Acc. Chem. Res. 1993,
26, 530e536; (b) Whitten, D. G. Acc. Chem. Res. 1993, 26, 502e509; (c)
Turro, N. J. Acc. Chem. Res. 2000, 33, 637e646; (d) Sivaguru, J.;
Natarajan, A.; Kaanumalle, L. S.; Shailaja, J.; Uppili, S.; Joy, A.;
Ramamurthy, V. Acc. Chem. Res. 2003, 36, 509e521; (e) Tung, C. H.;
Wu, L. Z.; Zhang, L. P.; Chen, B. Acc. Chem. Res. 2003, 36, 39e47.
3. (a) Keller, H.; Hatz, R. Handbook of Liquid Crystals, 1st ed.; Chemie:
Weinheim, 1980; (b) Wang, L.-Y.; Liao, S.-S. Liquid Crystal Chemistry;
Science: Beijing, 1988.
4. Xu, J.-X.; Liu, T.-Q.; Guo, R. Acta Phys.-Chim. Sin. 2003, 19, 364e367.
5. (a) Beck, J. S.; Vartuli, J. C.; Roth, W. J.; Leonowicz, M. E.; Kresge, C. T.;
Schmitt, K. D.; Chu, C. T.-W.; Olson, D. H.; Sheppard, E. W.; McCullen,
S. B.; Higgins, J. B.; Schlenker, J. L. J. Am. Chem. Soc. 1992, 114,
10834e10843; (b) Ciesla, U.; Froba, M.; Stucky, G.; Schuth, F. Chem.
¨
¨
Mater. 1999, 11, 227e234; (c) Jiang, X. C.; Xie, Y.; Lu, J.; Zhu, L. Y.;
He, W.; Qian, Y. T. Chem. Mater. 2001, 13, 1213e1218; (d) Rabatic,
B. M.; Pralle, M. U.; Tew, G. N.; Stupp, S. I. Chem. Mater. 2003, 15,
1249e1255.
6. (a) DePierro, M. A.; Guymon, C. A. Macromolecules 2006, 39, 617e626;
(b) DePierro, M. A.; Carpenter, K. G.; Guymon, C. A. Chem. Mater. 2006,
18, 5609e5617; (c) Lester, C. L.; Smith, S. M.; Jarrett, W. L.; Guymon,
C. A. Langmuir 2003, 19, 9466e9472; (d) McCormick, D. T.; Stovall,
K. D.; Guymon, C. A. Macromolecules 2003, 36, 6549e6558; (e) Lester,
C. L.; Colson, C. D.; Guymon, C. A. Macromolecules 2001, 34,
4430e4438; (f) Lester, C. L.; Smith, S. M.; Guymon, C. A. Macromole-
cules 2001, 34, 8587e8589; (g) Nees, D.; Wolff, T. Langmuir 1996, 12,
4960e4965.
7. (a) Nerbonne, J. M.; Weiss, R. G. J. Am. Chem. Soc. 1979, 101, 402e407;
(b) Hrovat, D. A.; Liu, J. H.; Turro, N. J.; Weiss, R. G. J. Am. Chem. Soc.
1984, 106, 5291e5295.
8. (a) Pirkle, W. H.; Rinaldi, P. L. J. Am. Chem. Soc. 1977, 99, 3510e3511;
(b) Verbit, L.; Halbert, T. R.; Patterson, R. B. J. Org. Chem. 1975, 40,
1649e1650; (c) Saeva, F. D.; Sharpe, P. E.; Olin, G. R. J. Am. Chem.
Soc. 1975, 97, 204e205; (d) Nakazaki, M.; Yamamoto, K.; Fujiwara, K.
Chem. Lett. 1978, 863e864.
3. Conclusion
The photochemical reaction of cyclohexyl phenyl ketone 1
within LC has been investigated to probe whether LC could be
used as a confined medium for selective photochemical reac-
tions. Studies on the product distributions of ketone 1 in the
absence and presence of electron donors reveal that LC not
only restricts the movement of the substrates and intermediates
but also encapsulates the substrates and electron donors to-
gether during photoirradiation. A comparison of the same re-
action in SDS micelle further evidence that LC provides
a much better constraint. By controlling the viscosity and close
contact between substrates and electron donors, the solution-
like LC can be used as a microreactor to direct the reaction
pathway of photochemical reactions.
9. (a) Cohen, S. G.; Chao, H. M. J. Am. Chem. Soc. 1968, 90, 165e173; (b)
Cohen, S. G.; Pardla, A.; Parsons, G. H. Chem. Rev. 1973, 73, 141e161;
(c) Lewis, F. D.; Johnson, R. W.; Johnson, D. E. J. Am. Chem. Soc. 1974,
96, 6090e6099; (d) Lewis, F. D.; Johnson, R. W. J. Am. Chem. Soc. 1972,
94, 8914e8916; (e) Padwa, A.; Eastman, D. J. Am. Chem.
Soc. 1969, 91, 462e467; (f) Stocker, J. H.; Kern, D. H. J. Chem. Soc.,
Chem. Commun. 1969, 204e205.
10. (a) Reynolds, J. L.; Erdner, K. R.; Jones, P. B. Org. Lett. 2002, 4,
917e919; (b) Shailaja, J.; Ponchot, K. J.; Ramamurthy, V. Org. Lett.
2000, 2, 937e940.
11. (a) Kalyanasundaram, K.; Thomas, J. K. J. Am. Chem. Soc. 1977, 99,
2039e2044; (b) Dong, D. C.; Winnik, M. A. Photochem. Photobiol.
1982, 35, 17e21.